Singleton: Difference between revisions

=={{header|Wren}}==

Although it's possible to create a singleton in Wren, you have to rely on no one calling the 'private' constructor directly. This is because there is currently no way to create a private method in Wren - all you can do is to suffix the name with an underscore to indicate by convention it's for internal use only.

In practice, it's unlikely anyone would bother; they'd just create a class with static methods and/or fields only which is effectively a singleton as there's only ever a single instance of a static field.

<lang ecmascript>class Singleton {

// Returns the singleton. If it hasn't been created, creates it first.

static instance { __instance == null ? __instance = Singleton.new_() : __instance }

// Private constructor.

construct new_() {}

// instance method

speak() { System.print("I'm a singleton.") }

}

var s1 = Singleton.instance

var s2 = Singleton.instance

System.print("s1 and s2 are same object = %(Object.same(s1, s2))")

s1.speak() // call instance method</lang>

{{out}}

<pre>

s1 and s2 are same object = true

I'm a singleton.

</pre>